Câu 2:
1: Khi x=9 thì \(A=\dfrac{-3}{3+5}=\dfrac{-3}{8}\)
2: \(B=\dfrac{2x+4\sqrt{x}-x+3\sqrt{x}-2+2-5\sqrt{x}}{x-4}=\dfrac{x+2\sqrt{x}}{x-4}=\dfrac{\sqrt{x}}{\sqrt{x}-2}\)
2: P=B/A
\(=\dfrac{\sqrt{x}}{\sqrt{x}-2}:\dfrac{-\sqrt{x}}{\sqrt{x}+3}=\dfrac{-\sqrt{x}-3}{\sqrt{x}-2}\)
P>-1/3
=>P+1/3>0
=>\(\dfrac{-\sqrt{x}-3}{\sqrt{x}-2}+\dfrac{1}{3}>0\)
=>\(\dfrac{-3\sqrt{x}-9+\sqrt{x}-2}{3\left(\sqrt{x}-2\right)}>0\)
=>(-2căn x-11)/3(căn x-2)>0
=>căn x-2<0
=>0<=x<4
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